Getter container



July 12, 1966 s. GARBE 3,260,356

GETTER CONTAINER Filed NOV. 2l, 1963 INVENTOR SIEGFRIED GAR BE BY M United States Patent O N Claims. (Cl. 206-.4)

The invention relates to a getter arrangement for or in vacuum vessels, especially electron tubes, which is enclosed in an envelope to prevent the absorption of gas from the vacuum vessel.

The term protective envelope is used herein to denote not only the closed but also the opened protective envelope in the finished vacuum vessel.

When -a getter is disposed in an unprotected condition within a vacuum vessel, in many cases, for example, in a prolonged pumping time, the getter, which has not yet been activated, is liable to be attacked or deteriorated by the gases evolved when the vessel is red and degassed.

It is already known to provide barium getters in the form of stable alloys. This has the additional advantage that the getters can be stored for a comparatively long period.

It is also known to enclose barium or a barium alloy within a closed container, part of the wall of the container consisting of a readily fusible foil of a metal such as, for example, magnesium or aluminium. Before activation the foil is opened by melting.

Such a foil cannot be used with non-vaporizing getters consisting of a finely powdered supply of large specific surface of a getter metal, which may be mixed with a metal preventing the tendency to sinter together, since the melting metal of the foil would penetrate into the powder, which in the non-activated state consists of the hydride of the getter metal, so that the getter would be poisoned.

In some cases, however, for example, in television display tubes or large transmitter tubes, such non-vaporizing getters are heated during the tiring and degassing process to a temperature of 300 C. or even to a higher temperature for a prolonged period of time. Consequently the greater part of the getter is already activated, so that due to its high pumping rate the getter is likely to absorb such an amount of the gases evolved that very little of the capacity of the getter is left and that on repeated activation the gases expelled may have a detrimental influence upon sensitive electrodes or particular layers.

Furthermore in getters consisting of a more or less compact mass of a non-vaporizing getter metal a protective metal foil cannot always be used since removal of the foil by melting may give rise to undesirable alloying.

According to the present invention, in a getter arrangement for or in vacuum vessels, especially electron tubes, which is enclosed in an envelope to prevent the absorption of gas from the vacuum vessel, the protective envelope consists of two apertured metal layers with an interposed -foil of a metal having 4a melting point lower than that of the apertured layers. After firing and degassing of the vessel the getter is activated by heating the envelope externally which results in the metal foil being melted. The melted metal foil Wets firstly the outer apertured metal layer and subsequently the inner apertured metal layer with the result that the melted metal is prevented from wetting the getter arrangement. According to the invention, the apertured metal layers preferably have such a composition, at least supercially, that they are capable of alloying with the metal of the foil. Substantially the only suitable material for the foil is aluminum, while for the apertured layers a choice may be made between copper-nickel alloy, nickel-plated copper nickel or nickelplated iron.

Although iiattened gauze may be used for the apertured metal layers, the most suitable material is what is known as expanded metal, since in this case the protective envelope after being opened by melting readily provides access to gases and furthermore may readily be made up from several parts by welding. Under certain circumstances part of the protective envelope may consist of non-apertured material.

A getter arrangement in accordance with the invention may contain within the protective envelope a non-activated non-vaporizing getter; however, alternatively there may be enclosed in the protective envelope a non-Vaporizing getter on the basis, for example, of hydride, which is activated completely or for the greater .part` This requires activation and enclosure of the getter in a special apparatus, for example, in a vacuum or in an argon atmosphere, as is already known, for example, for Vaporizing getters.

If, however, non-activated getters having a high specic surface are used, the protective envelope of the getter arrangement exerts a favourable influence upon the degassing process, since in the case of desorption of previously physically absorbed gases, for example water vapor, which may be produced by heating the still unactivated getter, this envelope prevents these gases from being liberated into the vacuum vessel. Owing to the large specific surface of the getter these amounts of gas may be far greater than the amounts liberated from the smaller surface of the vacuum vessel to be evacuated. When the vacuum vessel is cleaned by firing, these gases remain contained in the protective envelope and are again absorbed by the getter, which in the firing process at 300 C. is already partly activated, as long as the protective envelope is closed.

In order that the invention may readily be carried into effect, an embodiment thereof will now be described, by Way -of example, with reference to the accompanying diagrammatic drawing, in which:

FIG. 1 is a sectional View -of a getter arrangement with a closed protective envelope, and

FIG. 2 shows part of an opened protective envelope.

In FIG. l, a supply of powder 1 comprises 500 mgs. of grains having a mean diameter of 300 microns. T-he grains consist of a mixture of about equal parts by weight of zirconium hydride and powdered tungsten having a powder diameter of from l to 2 microns only. The larger grains are obtained by granulating a larger moulding pressed under low pressure from the line powder. The supply of lpowder 1 is accommodated in wire netting 2 of stainless steel from wires 30 microns thick with interstices of 30 microns. The bag 2 is annular, 8 mms. high, has a mean diameter of 16 rnms. and a thickness of 3 mms. The inner and outer layers 3 and 4 of the protective envelope are made of expanded copper nickel sheet having a thickness of 0.1 mm., an aluminium foil 5 having a thickness of 50 microns being sandwiched between them. The halves are welded to one another along their annular rims with the aid of copper nickel tapes 9 and 10. The arrangement is supported by two supports 8 of copper nickel tape having a thickness of 0.5 mm. The apertures in the layers 3 and 4 of expanded metal are denoted by 6 and 7.

FIG. 2 shows part of the protective envelope on an enlarged scale. By melting the foil 5 the partly coinciding apertures 3 and 4 are opened while the aluminum alloys with the nickel of the surface layers of the expanded copper nickel, as `indicated at 11.

It has been found that, if the supply of powder is activated simultaneously with the removal of the foil by melting, its capacity of absorbing metal is not adversely affected, and that the preceding degassing process in the 3 vacuum vessel does not inuence the gas-absorbing capacity.

What is claimed is:

`1. A getter device for a vacuum vessel comprising a sealed envelope containing a getter material, said envelope comprising two apertured metal layers separated by an imperforate foil of a metal having a lower melting point than that of the metal of the `apertured metal layers.

2. A getter device `for a vacuum vessel comprising a sealed envelope containing a getter material, said enve lope comprising two apertured metal layers separated by an imperforate rfoil of a metal having a lower melting point than that of the metal of the apertured metal layers, at least the surfaces of said apertured metal layers having a composition which forms an alloy upon heating with said foil.

3. A getter device for a vacuum vessel comprising a sealed envelope containing a getter material, said envelope comprising t-wo apertured nickel-containing metal layers separated by an imperforate aluminum foil having a lower melting point than that of the metal of the apertured metal layers.

4. A getter device as claimed in claim 3 in which the apertured metal `layers are constituted of a nickel alloy.

5. A getter device as claimed in claim -3 in which the apertured meta-l layers are constituted of nickel-plated iron.

6. A getter device as claimed in claim 3 in which the apertured metal layers are constituted off copper-nickel alloy.

7. A getter device for a vacuum vessel comprising a sealed envelope containing a getter material, said envelope comprising two apertured layers of expanded metal separated by an imperforatefoil of a metal having a lower melting point than that of the metal of the apertured metal layers.

8. A getter device for a vacuum vessel comprising a sealed envelope containing an activated getter material, said envelope comprising two apertured metal layers separated by an imperforate foil of a metal having a lower melting point than that of the metal of the apertured metal layers.

9. A getter device for a vacuum vessel comprising a sealed envelope containing a non-activated getter material, said envelope comprising t-wo apertured metal layers separated by an imperforate foil of a metal having a lower melting point than that of the metal of the apertured metal layers.

10. A getter -device rfor a vacuum vessel comprising a sealed envelope containing a getter material, said envelope comprising two apertured metal layers separated by a foil of an imperforate metal having a lower melting point than that of the metal of the apertured metal layers, said envelope opening upon heating by melting of the foil which t'iorms a residue -at the edges of the apertures.

References Cited by the Examiner UNITED STATES PATENTS 12,100,746 11/ 1937 Miller 206-4 X 2,336,138 12/1943 Hoorn 206-4 2,528,547 11/ 1950 Reilly 206-4 X 2,855,534 10/1958 Moubis.

LOUIS G. MANCENE, Primary Examiner. 

10. A GETTER DEVICE FOR A VACUUM VESSEL COMPRISING A SEALED ENVELOPE CONTAINING A GETTER MATERIAL, SAID ENVELOPE COMPRISING TWO APERTURED METAL LAYERS SEPARATED BY A FOIL OF AN INPERFORATE METAL HAVING A LOWER MELTING POINT THAN THAT OF THE METAL OF THE APERTURED METAL LAYERS, SAID ENVELOPE OPENING UPON HEATING BY MELTING OF THE FOIL WHICH FORMS A RESIDUE AT THE EDGES OF THE APERTURES. 